U.S. patent number 5,091,497 [Application Number 07/621,179] was granted by the patent office on 1992-02-25 for heat-curing polyether-polyester-polyurethane ureas.
This patent grant is currently assigned to Bayer Aktiengesellschaft. Invention is credited to Gerhard Grogler, Eduard Hansel, Heinrich Hess, Richard Kopp, Thomas Scholl.
United States Patent |
5,091,497 |
Grogler , et al. |
February 25, 1992 |
Heat-curing polyether-polyester-polyurethane ureas
Abstract
The present invention relates to heat-curable reaction systems
prepared by mixing (a) solid polyisocyanates (optionally
deactivated) having melting points above 80.degree. C., (b) OH-
and/or NH.sub.2 -terminated polyoxyalkylene polyethers that have
molecular weights of 400 to 10,000 and are liquid at room
temperature, (c) solid OH- and/or NH.sub.2 -terminated polyesters
that have molecular weights of 400 to 20,000 and are solid at room
temperature, and which are thoroughly distributed throughout the
mixture but are not homogeneously miscible with the polyether, (d)
optional low molecular weight chain-extending agents that contain
OH and/or NH.sub.2 groups and have a molecular weight of 62 to 399,
and (e) optional catalysts and other auxiliaries. The invention
further relates to a method for preparing elastomers, coating
compounds, sealing compounds, or adhesives by heat-curing the
heat-curable systems.
Inventors: |
Grogler; Gerhard (Leverkusen,
DE), Kopp; Richard (Cologne, DE), Hess;
Heinrich (Cologne, DE), Hansel; Eduard
(Wuppertal, DE), Scholl; Thomas (Meerbusch,
DE) |
Assignee: |
Bayer Aktiengesellschaft
(Leverkusen, DE)
|
Family
ID: |
6394882 |
Appl.
No.: |
07/621,179 |
Filed: |
November 30, 1990 |
Foreign Application Priority Data
Current U.S.
Class: |
528/76; 528/77;
528/78 |
Current CPC
Class: |
C08G
18/798 (20130101); C08G 18/707 (20130101); C08G
18/6618 (20130101); C08G 18/8038 (20130101); C09J
175/04 (20130101); C08G 18/0876 (20130101); C08G
18/4018 (20130101); C08G 2110/0033 (20210101) |
Current International
Class: |
C09J
175/04 (20060101); C08G 18/70 (20060101); C08G
18/40 (20060101); C08G 18/79 (20060101); C08G
18/66 (20060101); C08G 18/80 (20060101); C08G
18/00 (20060101); C08G 18/08 (20060101); C08G
018/32 () |
Field of
Search: |
;528/76,77,78 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Primary Examiner: Welsh; Maurice J.
Attorney, Agent or Firm: Gil; Joseph C. Henderson; Richard
E. L.
Claims
What is claimed is:
1. A heat-curable reaction system comprising a mixture of
(a) a solid polyisocyanate having a melting point above 80.degree.
C.,
(b) a linear or branched OH- and/or NH.sub.2 -terminated
polyoxyalkylene polyether that has a molecular weight of 400 to
10,000 and is liquid at room temperature,
(c) a solid linear or branched OH- and/or NH.sub.2 -terminated
polyester that has a molecular weight of 400 to 20,000 and is solid
at room temperature, wherein said polyester is thoroughly
distributed throughout the mixture but is not homogeneously
miscible with polyether (b), and
(d) optionally, a low molecular weight chain-extending agent that
contains OH and/or NH.sub.2 groups and has a molecular weight of 62
to 399.
2. A heat-curabble reaction system according to claim 1 wherein the
mixture additionally comprises
(e) optionally, catalysts and auxiliaries.
3. A heat-curable reaction system according to claim 1 wherein the
solid polyisocyanate is deactivated by adding an aliphatic diamine
in a sufficient quantity to form an anti-diffusion layer.
4. A heat-curable reaction system according to claim 3 wherein the
aliphatic diamine is used in the presence of at least a portion of
the polyether component (b).
5. A heat-curable reaction system according to claim 1 wherein the
solid polyisocyanate (a) is dimeric 2,4-diisocyanatotoluene or
3,3'-diisocyanato-4,4'-dimethyl-N,N'-diphenylurea.
6. A heat-curable reaction system according to claim 5 wherein the
solid polyisocyanate has a particle size of 0.1 to 150 .mu.m.
7. A heat-curable reaction system according to claim 5 wherein the
solid polyisocyanate has a particle size of 1 to 20 .mu.m.
8. A heat-curable reaction system according to claim 1 wherein the
polyether (b) has a molecular weight of 1,000 to 6,000.
9. A heat-curable reaction system according to claim 1 wherein the
polyether (b) has a molecular weight of 1,000 to 4,000.
10. A heat-curable reaction system according to claim 1 wherein the
polyester (c) has a molecular weight of 1,000 to 6,000.
11. A heat-curable reaction system according to claim 1 wherein the
polyester (c) is solid at room temperature and has a softening
point of 40 to 150.degree. C.
12. A heat-curable reaction system according to claim 1 wherein the
polyester (c) is solid at room temperature and has a softening
point of 40 to 130.degree. C.
13. A heat-curable reaction system according to claim 1 wherein the
polyester (c) is a fine powder having a particle size of from 10 to
200 .mu.m.
14. A heat-curable reaction system according to claim 1 wherein the
polyester (c) is a fine powder having a particle size of from 20 to
100 .mu.m.
15. In a method for the preparation of an elastomer, a coating
compound, a sealing compound, or an adhesive, the improvement
comprising curing a heat-curable reaction system according to claim
1 by heating said heat-curable reaction system to a temperature
above room temperature.
16. In a method for the preparation of an elastomer, a coating
compound, a sealing compound, or an adhesive, the improvement
comprising curing a heat-curable reaction system according to claim
1 by heating said heat-curable reaction system to a temperature of
from 100 to 150.degree. C.
Description
BACKGROUND OF THE INVENTION
This invention relates to heat-curing reactive systems comprising
mixtures of polyethers and polyesters that are not homogeneously
miscible with one another, optional OH-and/or NH.sub.2 -terminated
low molecular weight chain extenders, optional auxiliaries, and a
solid polyisocyanate having a melting point above 80.degree. C., in
which the polyester component is present in admixture as a solid
(such as powder or granules).
Polyurethanes based on polyoxyalkylene ethers are known to have
poorer mechanical properties than polyester-based polyurethanes.
Additional intermolecular secondary valence bonding forces occur in
polyester urethanes by virtue of the polar groups present. A
consequence of this is the crystallinity exhibited by many
polyesters, which ultimately determines the quality of the end
product. Thus, polyesters --or rather polyester urethanes --often
behave differently from polyether systems, even at high or low
temperatures. Polyester polyurethanes are used as high quality
products, particularly in those industrial fields where stringent
mechanical requirements must be satisfied.
Nevertheless, the majority of polyurethanes are based on
polyethers. Polyethers can be "refined" by modification in numerous
ways, so that the resulting end products also satisfy more
stringent practical requirements. Another important factor is that
polyethers are generally liquid at room temperature and, hence, are
much easier to process than, for example, solid polyesters. Other
advantages and disadvantages of both classes of these high
molecular weight compounds are well known to one skilled in the
art. There has been no shortage of attempts to eliminate or at
least reduce the disadvantages specific to polyethers or polyesters
by addition of polyesters or polyethers. Unfortunately, many
polyethers and polyesters are incompatible with one another because
of differences in their structural units. Emulsions or suspensions
which separate very quickly into two phases are obtained after
mixing of the two components, particularly when using polyesters
based, for example, on adipic acid and ethylene glycol or
1,4-butanediol.
When used in combination with chain-extending agents and
polyisocyanates, commercially available, inexpensive polyesters
give particularly high-quality elastomers. A two-phase system is
particularly difficult to process on an industrial scale. Despite
appropriate countermeasures (for example, use of special stirrers),
dosing errors can occur. In addition, phase separation occurs
during solidification, even after addition of the polyisocyanate.
These more or less distinct phases react with the isocyanate after
a relatively long reaction time, but a homogeneous, complete
reaction often does not occur. Because polyesters are generally
much more reactive than polyethers, preliminary reactions occur.
The more sluggishly reacting polyether can often appear as a
"greasy layer" on the surface of the moldings. The poly-addition
reaction can be accelerated by the use of suitable catalysts.
Because of a rapid increase in viscosity, however, the "pot life"
of the reaction mixtures is affected, so that processing by casting
is not possible. It has now surprisingly been found that the
disadvantages mentioned above do not arise when a powder-form
polyester that is solid at room temperature is suspended as the
polyester component in the polyether.
The resultant suspensions are pourable, spreadable, or paste-like,
depending on the quantity of solids added, and o solidify upon
heating. It has surprisingly been found in this regard that the
ordinarily incompatible polyethers and polyesters do not separate.
Instead, homogeneously cured moldings having a "dry surface" are
obtained after rapid hardening.
Microscopic examination of thin films has shown that the
polyurethane matrix consists of a polyether urethane or a polyester
urethane, depending on the polyether or polyester component. When a
matrix of polyether urethane is present, the s polyester urethane
is uniformly distributed throughout the polyether urethane matrix
as small beads (about 1-5 .mu.m). In When elongated, these beads
are longitudinally deformed in the direction of the force applied.
After relaxation, the starting condition is re-established.
SUMMARY OF THE INVENTION
Accordingly, the present invention relates to heat-curable reaction
systems comprising mixtures of
(a) solid polyisocyanates (optionally deactivated) having melting
points above about 80.degree. C.,
(b) linear or branched OH- and/or NH.sub.2 -terminated
polyoxyalkylene polyethers that have molecular weights of about 400
to about 10,000 (preferably 1,000 to 6,000 and more preferably
1,000 to 4,000) and are liquid at room temperature,
(c) solid linear or branched OH- and/or NH.sub.2 -terminated
polyesters that have molecular weights of about 400 to about 20,000
(preferably 1,000 to 6,000) and are solid at room temperature,
wherein said polyesters are thoroughly distributed throughout the
mixture but are not homogeneously miscible (that is, in one phase)
with polyether (b),
(d) optionally, low molecular weight chain-extending agents that
contain OH and/or NH.sub.2 groups and have a molecular weight of
about 62 to about 399, and
(e) optionally, known catalysts and other auxiliaries used in
polyurethane chemistry.
In the pre-cured state, the heat-curable reaction mixture contains
component (c) as a solid (preferably a finely divided solid such as
a fine powder or granules) that is well distributed during the
mixing process. When using finely divided powders, preferred
particle sizes range from about 10 to about 200 .mu.m (more
preferably, 20 to 100 .mu.m). The reactive components are used in
quantities such that an isocyanate index of about 50 to about 200
(preferably 90 to 135) is maintained.
DETAILED DESCRIPTION OF THE INVENTION
Suitable solid polyisocyanates (a) are those having a melting point
above about 80.degree. C., including, for example, 1,5-naphthalene
diisocyanate, dimeric 4,4'-diisocyanatodiphenyl-methane, dimeric
2,4-diisocyanatotoluene (dimeric 2,4-TDI, or "TT"),
3,3'-diisocyanato-4,4'-dimethyl-N,N'-diphenylurea (TDI urea
diisocyanate, or "TDIH"), and N,N!-bis[4-(4- or
2-iso-cyanatophenylmethyl)phenyl] ura. Dimeric
2,4-diisocyanato-toluene and
3,3'-diisocyanato-4,4'-dimethyl-N,N'-diphenylurea are particularly
preferred. 3,3'-Diisocyanato-4,4'-dimethyl-N,N'-diphenylurea can be
prepared, for example, by the reaction of two moles of
2,4-diisocyanatotoluene and one mole of water. The solid
polyisocyanates preferably have a particle size of about 0.1 to
about 150 .mu.m (more preferably 1 to 20 .mu.m).
When preparing the compositions of the invention, it is of
considerable advantage if the solid isocyanate is "deactivated"
(that is, stabilized) with an appropriate quantity of an aliphatic
diamine in the presence of at least a portion of polyether
component (b). The reaction of the aliphatic diamine on the surface
of the isocyanate particles results in the formation of a thin
polyurea shell which acts as an anti-diffusion layer. This shell is
destroyed upon heating and the components then react rapidly with
one another. This process, which is described, for example, in U.S.
Pat. No. 4,483,974, gives one-component systems which can be
hardened at any chosen time at temperatures in the range from about
100 to about 150.degree. C. In general, the process is carried out
by adding, as a powder or fine granules, the desired quantity of
solid polyester (c) that has a molecular weight of about 400 to
about 20,000 and is solid at room temperature to polyether polyol
(b) that has a molecular weight of about 400 to about 10,000 and is
liquid at room temperature. The resultant mixture is then
thoroughly homogenized by means of a stirrer. It is advisable to
add a small quantity of an aliphatic diamine to the suspension at
this stage to form an anti-diffusion layer on the surface of the
particles when the solid isocyanate is subsequently added. The
quantity of aliphatic diamine is selected to be just sufficient to
form such an anti-diffusion layer and can readily be determined by
one skilled in the art.
The polyester powder may also be externally mixed with the total
quantity of solid isocyanate and the resulting mixture added to the
polyether at a later stage. The polyether may optionally contain a
small quantity of aliphatic diamine to form an anti-diffusion
layer, as well as OH- or NH.sub.2 -terminated low molecular weight
chain-extending agents and other auxiliaries such as catalysts. All
isocyanate-reactive components must be taken into account for the
NCO balance.
The polyisocyanates are optionally "deactivated" by the action of
aliphatic polyamines having molecular weights of 32 to 399 and,
optionally, aliphatic polyamines having molecular weights of 400 to
8,000. Examples of suitable polyamines include ethylenediamine,
1-amino-3,3,5-trimethyl-5-aminomethylcyclohexane,
3,3'-dimethyl-4,4'-diaminodicyclohexyl-methane, diethylenetriamine,
and methyl nonanediamine.
Other suitable stabilizers include hydrazine, generally in the form
of hydrazine hydrate; (C.sub.1-6 alkyl)-substituted hydrazines,
such as methylhydrazine, ethyl hydrazine, (hydroxyethyl)hydrazine,
or N,N'-dimethylhydrazine; hydrazide-terminated compounds, such as
carbodihydrazide, ethylene bis-carbazinic ester,
.beta.-semicarbazidopropionic acid hydrazide, or isophorone
bis-semicarbazide. Other deactivating agents are described in
German Offenlegungsschriften 3,230,757 and 3,112,054.
Open-chain monocyclic or bicyclic amidines or guanidines containing
no isocyanate-reactive hydrogen atoms may also be used as
stabilizers for the isocyanate component. Examples of such
compounds include tetramethylguanidine, pentamethyl guanidine,
1,2-dimethyltetrahydropyrimidine, 1,8-diazabicyclo[5.4.0]
undec-7-ene, and 1,5-diazabicyclo-[4.3.0]non-4-ene. Further
examples of such amidines can be found in German
Offenlegungsschrift 3,403,500.
Compounds suitable for use as polyester component (c) include solid
polyesters that contain 2 to 8 (preferably 2 to 4) hydroxyl groups,
as well as, optionally, free carboxyl groups, and have molecular
weights of 400 to 20,000. Suitable o polyesters of this type are
solid at room temperature and have softening points of about 40 to
about 150.degree. C. Branched polyesters containing 2.1 to 4 OH
groups are particularly preferred. Such polyesters can be obtained
by polycondensation of hydroxycarboxylic acids or polymerization of
their lactones, optionally in the presence of branching agents
(that is, polyhydric alcohols and/or carboxylic acids). Examples
are hydroxycaproic acid and caprolactone. Suitable polyesters may
also be obtained by reaction of dihydric or polyhydric alcohols,
such as trihydric or tetrahydric alcohols, with dibasic or
polybasic carboxylic acids.
Instead of using the free polycarboxylic acids, it is also possible
to use corresponding polycarboxylic anhydrides or corresponding
polycarboxylic acid esters of lower alcohols, or mixtures thereof,
for the production of the polyesters. The polycarboxylic acids can
be aliphatic, cycloaliphatic, aromatic, and/or heterocyclic and can
optionally be substituted (for example, by halogen atoms), and/or
unsaturated. Examples of such carboxylic acids and derivatives
thereof include succinic acid, adipic acid, suberic acid, azelaic
acid, sebacic acid, dodecanedioic acid, diglycolic acid, phthalic
acid, isophthalic acid, hexahydrophthalic acid, phthalic anhydride,
tetrahydrophthalic anhydride, hexahydrophthalic anhydride,
tetrachlorophthalic anhydride, terephthalic acid, glutaric acid,
glutaric anhydride, maleic acid, maleic anhydride, fumaric acid,
trimellitic acid, pyromellitic acid, dimerized and trimerized
unsaturated fatty acid, dimerized unsaturated fatty acids (such as
oleic acid), terephthalic acid dimethyl ester, terephthalic acid
bis-glycol ester, citric acid, and endomethylene tetrahydrophthalic
anhydride.
Suitable polyhydric alcohols include ethylene glycol, diethylene
glycol, triethylene glycol, 1,2- and 1,3-propylene glycol,
dipropylene glycol, 1,4- and 2,3-butylene glycol, 1,6-hexanediol,
1,8-octanediol, neopentyl glycol,
1,4-bis-(hydroxymethyl)cyclohexane, 2-methyl-1,3-propanediol,
glycerol, trimethylolpropane, 1,2,6-hexanetriol, 1,2,4-butanetriol,
trimethylolethane, pentaerythritol, tricyclododecane diol,
hydroquinone bis(hydroxyethyl) ether,
2,2-bis(hydroxyphenyl)-propane bis(hydroxyethyl) ether, quinitol,
mannitol, sorbitol, formitol, and methyl glycoside.
To prepare relatively high molecular weight polyesters having
molecular weights of about 5,000 to about 20,000 and softening
points (ring and ball method) of, preferably, about 70 to about
150.degree. C., terephthalic acid or isophthalic acid is used in a
quantity of 20 to 70 mole-%, based on the amount of the
polycarboxylic acid component. To produce polyesters having lower
molecular weights of about 400 to about 5,000 and softening points
of about 40 to about 100.degree. C., any of the other
polycarboxylic acids discussed above (particularly adipic acid) may
also be used in essentially any quantities based on the amount of
the polycarboxylic acid component. The preparation of such
polyesters is known and is described, for example, in Houben-Weyl,
Methoden der organischen Chemie. Vol. 14/2, Thieme-Verlag,
Stuttgart, 1961.
Other polyester components suitable for use according to the
invention include those containing aliphatic or aromatic terminal
amino groups that can be obtained by hydrolysis, preferably basic
hydrolysis, of corresponding NCO prepolymers based on relatively
high molecular weight polyhydroxyl compounds and excess aliphatic
or aromatic diisocyanates.
Examples process can be found in German Offenlegungsschriften
2,948,419, 3,039,600, and 3,112,118 and European Patent
Applications 61,627, 71,132, and 71,139. The first of these
patents, German Offenlegungsschrift 2,948,419, also mentions other
known processes for the preparation of relatively high molecular
weight amino compounds. The process according to these patents is
concerned not only with polyether amines, but also with polyester,
polyacetal, polythioether, or polycaprolactone polyamines
(preferably difunctional or trifunctional polyamines) that contain
urethane groups (from the reaction of the corresponding relatively
high molecular weight polyhydroxyl compounds with the excess
polyisocyanates) and that bear amino groups at the residue of what
had been the polyisocyanate. The aromatic polyamines of relatively
high molecular weight, however, may also be obtained by other
methods, for example, by reaction of NCO prepolymers with excess
quantities of hydrazine, aminophenyl ethylamine, or other diamines
in accordance with German Auslegeschrift 1,694,152. Another
possible synthesis is described in French Patent 1,415,317,
according to which the NCO prepolymers are converted into N-formyl
derivatives by reaction with formic acid, followed by
saponification. The reaction of NCO prepolymers with sulfamic acid
in accordance with German Auslegeschrift 1,155,907 also gives
polyamines of relatively high molecular weight.
The isocyanate-reactive suspension medium used to suspend the solid
(optionally stabilized) polyisocyanates and the solid (preferably
powder-form) polyesters includes a relatively high molecular weight
liquid polyol and/or polyamine (i.e., component (b)), optionally in
admixture with a low molecular weight liquid polyol and/or
polyamine (i.e., optional component (d)).
Suitable relatively high molecular weight polyols (b) having a
molecular weight in the range from about 400 to about 10,000
include polyethers and polythioethers containing at least 2
(preferably 2 to 4) hydroxyl groups and generally having a
molecular weight of 400 to 8,000 that are known for the preparation
of homogeneous and cellular polyurethanes. Examples of such
polyethers and polythioethers can be found, for example, in German
Offenlegungsschriften 2,920,501, 2,854,384, and 3,230,757.
Polyhydroxyl compounds already containing urethane or urea groups
and optionally modified natural polyols, such as castor oil,
carbohydrates, or starch, may also be used. Adducts of alkylene
oxides with phenol-formaldehyde resins or with urea-formaldehyde
resins are also suitable for use according to the invention.
Hydroxyl-terminated polybutadienes are also suitable for use in
accordance with the invention because they give particularly
elastic and hydrolysis-stable products. Polyhydroxyl compounds
containing high molecular weight polyadducts or polycondensates or
polymers in finely dispersed or even dissolved form may also be
used.
Polyadduct-containing polyhydroxyl compounds are obtained by
carrying out polyaddition reactions (for example, reactions between
polyisocyanates and aminofunctional compounds) or polycondensation
reactions (for example, between formaldehyde and phenols and/or
amines) in situ in the above-mentioned hydroxyl-containing
compounds.
Polyhydroxyl compounds modified by vinyl polymers, as obtained, for
example, by polymerization of styrene and acrylonitrile in the
presence of polyethers or polycarbonate polyols, are also suitable
for use according to the invention.
Representatives of these compounds that can be used according to
the invention are described, for example, in Hiqh Polymers. Vol.
XVI; "Polyurethanes, Chemistry and Technology", by Saunders and
Frisch, Interscience Publishers, New York, London, Vol. I, 1962,
pages 32-42, 44, and 54, and Vol. II, 1964, pages 5-6 and 198-199;
Kunststoff-Handbuch, Vol. VII, Vieweg-Hochtlen, Carl-Hanser-Verlag,
Munich 1966, pages 45-71, and German Offenlegungsschriften
2,854,384 and 2,920,501.
Other suitable polyols include polymers containing hydroxyl groups,
such as copolymers of olefinically unsaturated monomers and
olefinically unsaturated monomers containing active hydrogen,
described, for example, in European Patent Application 62,780, page
5 and the Examples. Such compounds are preferably used for sealing
compounds, fillers, adhesives, or undersealing compounds.
Mixtures of the above-mentioned compounds containing at least two
isocyanate-reactive hydrogen atoms can, of course, also be
used.
Low molecular weight chain-extending agents or crosslinking agents
may also be used as polyols (d) optionally present in the
suspensions. Suitable chain-extending agents or crosslinking agents
include, preferably, at least difunctional compounds that contain
hydroxyl groups attached to aliphatic and/or cycloaliphatic groups
and have molecular weights of about 62 to about 399. Preferred
compounds of this type include low molecular weight diols
containing hydroxyl groups attached to aliphatic or cycloaliphatic
groups and having a molecular weight in the range from 62 to
399.
Suitable low molecular weight chain-extending or crosslinking
agents generally contain 2 to 8 (preferably 2 to 4 and more
preferably 2)hydroxyl groups. Mixtures of different compounds may,
of course, also be used. Examples of such compounds include
ethylene glycol, diethylene glycol, triethylene glycol,
tetraethylene glycol, trimethylene glycol, 2,3- and/or
1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, neopentyl glycol,
1,4-bis(hydroxyethyl)cyclohexane, 1,4-dihydroxycyclohexane,
tetephthalic acid bis(.beta.-hydroxyethyl) ester,
1,4,3,6-dianhydrohexitols, 1,4-monoanhydrotetritols, propylene
glycol, dipropylene glycol, tripropylene glycol, tetrapropylene
glycol, bis(2-hydroxyethyl)hydroquinone, and
bis(2-hydroxyethyl)resorcinol. Suitable polyfunctional compounds
include trimethylolpropane, trimethylolethane, 1,26-hexanetriol,
glycerol, pentaerythritol, quinitol, mannitol, sorbitol, castor
oil, and formose or formitol.
Diols or polyols containing tertiary amines, such as
N-methyldiethanolamine, triethanolamine, or N,N'-bis(hydroxyethyl)
piperazine, are also suitable.
It is also possible to use diols containing additional groups, for
example adipic acid bis(2-hydroxyethyl) ester, terephthalic acid
bis(2-hydroxyethyl) ester, diol urethanes, diol ureas, or polyols
containing sulfonate and/or phosphonate groups. Examples include
1,6-hexamethylene bis(2-hydroxyethyl urethane),
4,4'-diphenylmethane bis(2-hydroxyethyl urea), and the adduct of
sodium bisulfite with 1,4-butanediol or alkoxylation products
thereof. Other low molecular weight compounds are described in
detail in German Offenlegungsschrift 2,854,384.
The low molecular weight and relatively high molecular weight
polyols described above may optionally be modified by preliminary
reaction with a substoichiometric quantity of polyisocyanate.
Suitable polyisocyanates for this purpose include aliphatic,
cycloaliphatic, araliphatic, aromatic, and/or heterocyclic
polyisocyanates of the type described, for example, in German
Offenlegungsschrift 2,920,501 at pages 12 to 16. In general, it is
particularly preferred to use polyisocyanates readily obtainable on
an industrial scale, such as 2,4- and 2,6-toluene diisocyanate and
mixtures of these isomers ("TDI"), polyphenyl polymethylene
polyisocyanates of the type obtained by phosgenation of
aniline-formaldehyde condensates ("crude MDI"), 4,4'- and/or
2,4'-diphenylmethane diisocyanate, 1,6-hexamethylene diisocyanate,
1-isocyanato- 3,3,5-trimethyl-5-isocyanatomethylcyclohexane, and
perhydro-2,4'- and/or -4,4'-diphenylmethane diisocyanate.
Also suitable as the isocyanate-reactive suspension medium used to
suspend the solid (optionally stabilized) polyisocyanates and the
solid (preferably powder-form) polyesters are relatively high
molecular weight liquid aromatic and/or aliphatic polyamines,
optionally in admixture with a low molecular weight liquid aromatic
and/or aliphatic polyamine. Relatively high molecular weight
aliphatic and/or relatively high molecular weight or low molecular
weight aromatic polyamines are preferred. Low molecular weight
aliphatic polyamines can be present as stabilizers in at most small
quantities; relative large quantities of free, low molecular weight
aliphatic polyamines would result in overstabilization. Only low
molecular weight, aliphatic polyamines chemically bound in the form
of polyureas may be present in relatively large quantities.
The relatively high molecular weight polyamines containing aromatic
amino groups and having a molecular weight in the range from about
400 about 8,000 that are used according to the invention include,
preferably, polyamines of the type obtainable by hydrolysis,
preferably basic hydrolysis, of corresponding NCO prepolymers based
on relatively high molecular weight polyhydroxyl compounds and
excess aromatic diisocyanates. Examples of this process can be
found in German Offenlegungsschriften 2,948,419, 3,039,600, and
3,112,118 and European Patent Applications 61,627, 71,132, and
71,139. The first of these patents, German Offenlegungsschrift
2,948,419, also mentions other known processes for the preparation
of relatively high molecular weight amino compounds. The process
according to these patents is concerned is concerned mainly with
polyether amines (preferably difunctional or trifunctional
polyamines) that contain urethane groups (from the reaction of the
corresponding relatively high molecular weight polyhydroxyl
compounds with the excess polyisocyanates) and that bear amino
groups at the residue of what had been the polyisocyanate. The
aromatic polyamines of relatively high molecular weight, however,
may also be obtained by other methods, for example, by reaction of
NCO prepolymers with excess quantities of hydrazine, aminophenyl
ethylamine, or other diamines in accordance with German
Auslegeschrift 1,694,152. Another possible synthesis is described
in French Patent 1,415,317, according to which the NCO prepolymers
are converted into N-formyl derivatives by reaction with formic
acid, followed by saponification. The reaction of NCO prepolymers
with sulfamic acid in accordance with German Auslegeschrift
1,155,907 also gives polyamines of relatively high molecular
weight.
Suitable relatively high molecular weight polyamino compounds
containing aliphatic amino groups and having a molecular weight of
about 400 to about 8,000 (preferably 1,000 to 4,000) include those
of the type obtained by reductive amination of polyoxyalkylene
glycols with ammonia in accordance with Belgian Patent 634,741 and
U.S. Pat. No. 3,654,370. Other relatively high molecular weight
polyoxyalkylene polyamines may be obtained by the methods listed in
"Jeffamine, Polyoxypropylene Amines", a company publication of the
Texaco Chemical Co., 1978, for example, by hydrogenation of
cyanoethylated polyoxypropylene glycols (German Offenlegungsschrift
1,193,671), by amination of polypropylene glycol sulfonic acid
esters (U.S. Pat. No. 3,236,895), by treatment of a polyoxyalkylene
glycol with epichlorohydrin and a primary amine (French Patent
1,466,708), or by reaction of NCO prepolymers with enamines,
aldimines, or ketimines containing hydroxyl groups and subsequent
hydrolysis in accordance with German Offenlegungsschrift 2,546,536.
Other suitable relatively high molecular weight aliphatic diamines
and polyamines include polyamines obtainable in accordance with
German Offenlegungsschriften 2,948,419, 3,039,600, and 3,112,118,
and European Patent Applications 61,627, 71,132, and 71,139 by
alkaline hydrolysis of NCO prepolymers (based on aliphatic
diisocyanates) with bases at the carbamate stage.
The process according to German Offenlegungsschrift 2,948,419 and
the other cited literature references discussed above are concerned
mainly with polyether polyamines or polythioether polyamines
(preferably difunctional or trifunctional polyamines) that contain
urethane groups (from the reaction of the corresponding relatively
high molecular weight polyhydroxyl compounds with the excess
polyisocyanates) and that bear amino groups at the residue of what
had been the polyisocyanate. The aromatic polyamines of relatively
high molecular weight, however, may also be obtained by other
methods, for example, by reaction of NCO prepolymers with excess
quantities of hydrazine, aminophenyl ethylamine, or other diamines
in accordance with German Auslegeschrift 1,694,152. Another
possible synthesis is described in French Patent 1,415,317,
according to which the NCO prepolymers are converted into N-formyl
derivatives by reaction with formic acid, followed by
saponification.
These relatively high molecular weight aliphatic polyamines may be
used both as stabilizers for the polyisocyanate component and as a
further component of the suspension medium.
Low molecular weight aromatic diamines having a molecular weight in
the range from about 108 to about 399 may be used as
chain-extending agents. The term aromatic polyamine is also
understood to include amines which contain the amino group attached
to heterocyclic radicals of aromatic character. Examples of
suitable aromatic polyamines include p-phenylene-diamine, 2,4-
and/or 2,6-toluenediamines, diphenylmethane-4,4'-and/or -2,4'-
and/or -2,2'-diamines, 3,3'-dichloro-4,4'-diaminodiphenyl-methanes,
3'-(C.sub.1-4 alkyl)-4,4' diaminodiphenylmethanes,
3,3'-di(C.sub.1-4 alkyl)-4,4'-diaminodiphenylmethanes,
3,3',5,5'-tetra(C.sub.1-4 alkyl)-4,4'-diphenylmethanes,
4,4'-diaminodiphenyl sulfides, sulfoxides, or sulfones, diamines
containing ether groups according to German Offenlegungsschriften
1,770,525 and 1,809,172 (U.S. Pat. Nos. 3,654,364 and 3,736,295),
2-halo-1,3-phenylenediamines optionally substituted in the
5-position (German Offenlegungsschriften 2,001,772, 2,025,896, and
2,065,869), bis-anthranilic acid esters (German
Offenlegungsschriften 2,040,644 and 2,160,590), 2,4-diaminobenzoic
acid esters according to German Offenlegungsschriften 2,025,900,
and toluenediamines substituted by one or two C.sub.1-4 alkyl
groups. Particularly preferred chain-extending agents are 3,
5-diethyl-2,4- and/or -2,6-diaminotoluene (more particularly, their
technical (80/20) or (65/35) isomer mixtures), asymmetrically
tetraalkyl-substituted diamino-diphenyl methanes such as
3,5-diethyl-3',5'-diisopropyl-4,4'-diaminodiphenylmethane and
isomer mixtures thereof according to German Offenlegungsschriften
2,902,090, 4,4'-diaminobenzanilide, 3,5-diaminobenzoic acid alkyl)
(C.sub.1-4 alkyl) ester, 4,4'-and/or 2,4'-diaminodiphenylmethane,
and naphthylene-1,5'-diamine.
Mixtures of the above-mentioned polyhydroxyl compounds and
polyamino compounds can, of course, be used.
Typical polyurethane catalysts may optionally be used. Of these,
tertiary amines or metal catalysts are particularly preferred.
Suitable tertiary amine catalysts include tertiary amines, such as
triethylamine, tributylamine, N,N,N',N'-tetramethyl
ethylenediamine, 1,4-diazabicyclo[2.2.2]octane,
N,N-dimethylbenzylamine, and N,N-dimethylcyclohexylamine.
Suitable organometallic catalysts include organotin compounds and
organolead compounds. Preferred organotin compounds include tin(II)
salts of carboxylic acids, such as tin(II) ethylhexoate and tin(II)
stearate, and dialkyl tin salts of carboxylic acids, such as
dibutyltin dilaurate or dioctyltin diacetate. Preferred organolead
compounds include lead(II) salts of carboxylic acid, such as
lead(II) naphthenate, lead(II) ethylhexoate, lead(II) stearate, and
lead(II) bis(diethyl dithiocarbamate).
Other suitable catalysts and information on their mode of action
can be found in Kunststoff-Handbuch, Vol. VII, edited by Vieweg and
Hochtlen, Carl-Hanser-Verlag, Munich 1966, for example, on pages
96-102, and German Offenlegungsschrift 3,230,757.
The catalysts are generally used in a quantity of from about 0.001
to about 10% by weight, based on the composition as a whole.
The generally inorganic auxiliaries and additives optionally
present include dyes or pigments and fillers, such as heavy spar,
chalk, silica flour, kieselguhr, silica gel, precipitated silicas,
pyrogenic silicas, gypsum, talcum, active carbon, carbon black, and
metal powders.
Other suitable auxiliaries and additives include o reaction
retarders, for example acidic substances such as hydrochloric acid,
organic acid halides, or organic acids; known flameproofing agents,
such as tris(chloroethyl) phosphate or ammonium phosphate and
polyphosphate; stabilizers against the effects of ageing and
weathering, such as phenolic antioxidants and light stabilizers;
plasticizers; and fungistatic and/or bacteriostatic agents.
Suitable fillers include fibrous materials (i.e., any known fibrous
reinforcing materials) such as glass fibers or fibers based on an
organic polymer. Suitable organic polymers include polyesters, such
as polyethylene terephthalate, or, preferably, aromatic polyamides,
such as m-phenylene/isophthalic acid polyamide or poly-p-phenylene
terephthalamide or even polycaprolactam. These fibrous materials
may be present, for example, in the form of mats, rovings,
full-length fibers, nonwovens, woven fabrics, or a random mixture
of staple fibers. Glass fibers that have been sized to make them
receptive to polyurethanes are preferred. The quantity of filler to
be incorporated depends on the desired improvement in the
mechanical properties and is generally between about 5 and about
60% by weight fibers.
When cellular polyurethanes are to be produced by the process of
the invention, water and/or readily volatile organic substances are
used as blowing agents. Suitable organic blowing agents include
acetone, ethyl acetate, methanol, ethanol, halogen-substituted
alkanes (such as methylene chloride, chloroform, ethylidene
chloride, vinylidene chloride, monofluorotrichloromethane,
chlorodifluoromethane, and dichlorodifluoromethane), butane,
hexane, heptane, and diethyl ether.
Further examples of blowing agents and information on the use of
blowing agents can be found in Kunststoff-Handbuch. Vol. VII,
edited by Vieweg and Hochtlen, Carl-Hanser-Verlag, Munich 1966, for
example, on pages 108, 109, 453, 455, and 507-510.
Surface-active additives (emulsifiers and foam stabilizers) may
also be used. Suitable emulsifiers include sodium salts of castor
oil sulfonates or even of fatty acids or salts of fatty acids with
amines, such as diethylamine oleate or diethanolamine stearate.
Alkali or ammonium salts of sulfonic acids, for example, of
dodecylbenzenesulfonic acid or dinaphthylmethanedisulfonic acid, or
of fatty acids, such as ricinoleic acid, or of polymeric fatty
acids, may also be used as surface-active additives.
Suitable foam stabilizers are, preferably, watersoluble polyether
siloxanes. The structure of these compounds is generally such that
a copolymer of ethylene oxide and propylene oxide is attached to a
polydimethylsiloxane residue. Foam stabilizers such as these are
described, for example, in U.S. Pat. No. 2,764,565.
Known cell regulators, such as paraffins or fatty alcohols or
dimethylpolysiloxanes, as well as pigments or dyes, may also be
used.
Further examples of suitable surface-active additives and foam
stabilizers, cell regulators, reaction retarders, o stabilizers,
flameproofing agents, plasticizers, dyes and fillers, fungistatic
and bacteriostatic agents, as well as information on the use of
such additives and the way in which they work, can be found in
Kunststoff-Handbuch. Vol. VI, edited Vieweg and Hochtlen,
Carl-Hanser-Verlag, Munich 1966, for example, on pages 103-113 and
German Offenlegungsschriften 2,854,384 and 2,920,501.
The reactive polyurethane mixtures according to the invention may
be used for the production of elastomeric moldings, adhesives,
sealing, and coating compounds.
The reactive polyurethane mixtures obtained according to the
invention are pourable, knife-coatable, or spreadable at room
temperature, depending on the viscosity and melt behavior of the
starting components and on the quantitative ratio of o solid
powder-form constituents to liquid constituents. These reactive
mixtures are suspensions of a solid polyisocyanate stabilized by a
polyadduct coating in the polyol and any optional polyamine
component. These mixtures are hardened by application of heat at
temperatures above room temperature (preferably from 100 to
150.degree. C.). The processing of the heat-curable systems of the
invention depends on their nature and the particular technical
problem to be solved. They may be applied, for example, by hand or
by a suitable delivery or transport unit, such as a cartridge or a
knife, to any desired substrates, for example, bare or precoated
metals or alloys of such metals, to plastic parts, to various
industrial articles made from metals, glass, ceramics, or plastics
(which may, for example, also be fiber-reinforced), and to textile
substrates, such as nonwovens, knitted fabrics, and woven fabrics,
(skiver) leather, matrices (for example, suede leather-silicone
matrices), or temporary supports (for example, release papers).
When so applied, these mixtures form coatings or finishes and may
be cured at elevated temperature (i.e., temperatures above room
temperature, preferably from 100 to 150.degree. C.), optionally
after further handling or industrial processing steps.
When blowing agents are used, it is possible to produce cellular
polyurethanes optionally having an integral density structure.
Surface coatings, impression molds or moldings may also be produced
by dip-coating processes.
The following examples further illustrate details for the
preparation of the compositions of this invention. The invention,
which is set forth in the foregoing disclosure, is not to be
limited either in spirit or scope by these examples. Those skilled
in the art will readily understand that known variations of the
conditions and processes of the following preparative procedures
can be used to prepare these compositions. Unless otherwise noted,
all temperatures are degrees Celsius and all parts and percentages
are parts by weight and percentages by weight, respectively.
EXAMPLES
Example 1 (Comparison Example)
A trifunctional liquid polypropylene glycol ether (molecular weight
3,000, OH number 56) (100 g) was mixed with 100 g of a solid
powder-form polyester of adipic acid and ethylene glycol (molecular
weight 2,000, OH value 56). The mixture was then heated to
approximately 50 to 60.degree. C. After a short time, an emulsion
of molten polyester in the polyether was obtained. The two
components are immiscible with one o another. After addition of 0.1
g of lead octoate (Octa-Soligen Pb 24, a product of Borchers) and
34.8 g of dimeric TDI ("TT"), the reaction mixture was degassed
with stirring for 15 to 30 minutes under an aspirator vacuum. The
reaction mixture was then poured into a mold and heated for 2 to 3
hours at 120.degree. C. Rapid initial crosslinking was observed,
reaching an end point after a time. An only partly crosslinked end
product, in which a distinctly visible film of unchanged
polypropylene glycol ether was situated on the surface, was
ultimately obtained. No subsequent crosslinking occurred, even at
relatively high temperatures.
EXAMPLE 2 (ACCORDING TO THE INVENTION)
When the mixture of 100 g of the liquid polypropylene glycol ether
and 100 g of the powder-form polyester described in Example 1 was
not heated to 50 to 60.degree. C., the suspension behaved
differently after the addition of lead octoate and dimeric TDI.
When the mixture was then heated to 120 to 130.degree. C., a fully
crosslinked molding having a smooth, homogeneous surface was
obtained after 2 to 3 hours.
EXAMPLE 3
Lead octoate (0.1 g) and 0.15 g LAROMIN C
(bis-(3-methyl-4-aminocyclohexyl)methane, a product of BASF) were
added to 100 g of a trifunctional polypropylene glycol ether
(molecular weight 3,000, OH value 56). A powder-form NH.sub.2
-terminated polyester (NH value 48) (100 g) prepared by known
methods (e.g., in accordance with European Patent Application
219,035) by alkaline hydrolysis of a preadduct of 1 mole of
polyadipate (prepared using ethylene glycol and 1,4-butanediol as
the esterification alcohol) and 2 mole of 2,4-diisocyanatotoluene
(TDI) was then homogeneously mixed with the above polyether
component. The temperature during this mixing step did not exceed
the melting temperature or softening temperature of the polyester.
After the further addition of 32.5 g of dimeric TDI, a liquid and
readily pourable suspension was obtained and could be stored
indefinitely at room temperature because of the formation of an
anti-diffusion layer on the surface of the TT particles (polyurea
shell by reaction of LAROMIN C with TT). The reaction mixture was
then degassed under aspirator vacuum and poured into a suitable
mold coated with release agent. The mixture hardened at a
temperature of 120 to 130.degree. C. and the molding could be
removed from the mold about 1 hour after hardening. After further
heating for 2 to 3 hours at 120.degree. C., a homogeneous elastomer
having the following mechanical properties was obtained:
Modulus (100%) (MPa) 7.5
Tensile strength (MPa) 22.0
Elongation at break (%) 500
Tear propagation resistance (KN/m) 34.5
Elasticity (%) 52
Hardness, Shore A 86
When, by contrast, the reaction mixture was heated before hardening
to a temperature above the melting point of the NH.sub.2
-terminated component, two immiscible liquid phases were formed and
immediately separated. Subsequent crosslinking at 120 to
130.degree. C. led to an inhomogeneous and only partly crosslinked
product which, in addition, had an oily layer of the polypropylene
glycol ether on the surface of the molding. Products such as these
are totally unsuitable for coating materials or adhesives where
firm adhesion to the substrate is necessary.
EXAMPLES 4 to 6
GENERAL PROCEDURE FOR THE PREPARATION OF ADHESIVE CONTAINING
OH-FUNCTIONAL POWDER-FORM FILLERS
The above-mentioned quantities of the finely ground polymer are
added with continued stirring at room temperature or at moderately
elevated temperature (<50.degree. C.) to a suspension of a
retarded polyisocyanate in a mixture of low molecular weight
polyhydroxy and/or polyamino compounds having a viscosity (as
measured at room temperature in accordance with DIN 53 019) of 0.1
to 250 Pa.multidot.s, preferably 1 to 10 Pa.multidot.s, until a
macroscopically homogeneous mixture is formed.
Stirrers and mixers having rotating stirring elements, such as
anchor stirrers or helical stirrers or even Z or sigma kneaders,
are suitable for the preparation of s relatively large quantities
of the mixtures according to the invention.
GENERAL PROCEDURE FOR THE APPLICATION OF THE MIXTURES ACCORDING TO
THE INVENTION AS ADHESIVES
The mixtures according to the invention are applied to one or both
of the parts to be bonded at temperatures below 50.degree. C.,
preferably at room temperature.
If the reactivity and thermal stability of the mixtures allow,
application temperatures above 50.degree. C. are also possible.
BONDING
SMC platelets (SMC 109, a product of Bayer AG, Leverkusen, Germany)
that are 4 mm thick and 20 mm wide and 40 mm long are bonded with a
10-mm overlay by coating one SMC platelet with the mixture of the
invention on this overlay surface and by placing a second,
optionally uncoated platelet thereon with the described overlay. A
third SMC platelet of the same dimensions is used both as a support
and as a fixing aid for avoiding changes in the overlay during the
curing process. A 200-.mu.m thick metal distance plate lying on
this third SMC platelet (where it acts as an intermediate layer
between the support and the applied SMC platelet) produces a
constant glueline thickness of 200 .mu.m.
CHARACTERISTICS OF THE FRACTURE TYPE OF THE GLUELINE
An A-fracture is the term used to describe the fracture type in
which separation occurs at the adhesive-adherend interface.
A K-fracture is a fracture within the glueline.
MF (material failure) signifies failure of the adherend material
under tensile shear testing.
CURING THE GUIDELINES
Heat must be applied to produce the final bond strengths. This
means increasing the temperature in the glueline and exceeding a
minimum temperature for a specified time, generally 10 seconds to
60 minutes and preferably 30 seconds to 20 minutes. The temperature
and the heating time depend on the formulation determined in
advance by the user and the adherend material.
In any event, however, a temperature above the formulation-specific
"thickening temperature" of the retarded polyisocyanate must be
determined in advance for the predetermined curing time in
accordance with known methods (e.g., German Offenlegungsschrift
3,403,499, believed to correspond to U.S. Pat. No. 4,595,445).
Examples of formulations for one-component polyurethane adhesives
containing an additon of OH-functional powder-form fillers are
shown in the following Table.
TABLE ______________________________________ Ex. 4 Ex. 5 Ex. 6 (%
by (% by (% by weight) weight) weight)
______________________________________ 2,2-bis(4-hydroxyphenyl)-
22.0 21.3 20.0 propane-started polyoxypro- pylene ether diamine (MW
1,000) 2,2-bis(4-hydroxyphenyl)- 29.0 27.8 26.2 propane-started
polyoxypro- pylene ether diol (MW 550)
2,4-diamino-3,5-diethyltoluene 2.5 2.5 2.4 Dimeric TDI 36.0 36.0
36.0 Lead octoate 0.2 0.2 0.2 4,4'-diamino-3,3'-dimethyl- 0.2 0.2
0.2 dicyclohexylmethane Hydroxypolyester (OH number 9.9 12.0 15.0
approx. 50) (m.p. ca. 100.degree. C.) SMC/SMC tensile shear
strength 10.25 9.6 9.35 after curing for 30 mins at 130.degree. C.
(DIN 53 283) (average value from 5 measurements) (N/mm.sup.2)
SMC/SMC heat failure 181.degree. C. 186.degree. C. 188.degree. C.
(ASTM D 4498) ______________________________________
* * * * *